Electrical resistance.



' No Drawing.

UNITED strAr s Jomve. CLEMENS, or BUEEALo, NEW YORK.

ELECTRICAL RESISTANCE.

To all whom it may concern;

Be it known that I,-JoHN G. CLEMENS, a citizen of the United States, residing at Buffalo, in the county of Erie and State of New York, have invented certain new and useful Improvements in Electrical Resistances, of which the following is a specification.

My invention relates to new and useful improvements in electrical resistances, and has for its primary object the provision of an electrical resistance of such a character that the resistance which it will offer to passage of current will gradually decrease as current flows through it and it becomes heated thereby.

More specifically my invention consists 1n a novel composition of matter including'a binder of non-current conducting capacity, a quantity of current conducting material and a quantity of current conducting material having high resistive powers. In this connection a still further object of my inven- .tion resides in providing a composition of this character which may be molded to shape and subsequently fired so that it may be formed into blocks, rods or other convenlent shape.

Broadly speaking my improved composition preferably consists of clay, iron and carborundum mixed in suitable proportions, molded and fired. In making the composition I take clay of ordinary or any preferred type and pulverize it into a very fine smooth powder.

I also pulverize iron, in the form of filings or in other convenient shape into a very fine, smooth powder and mix the pulverized clay and iron thoroughly. I then add to this mixture carborundum in small grains and again thoroughly mix the mass when it is ready for molding. Water is added to the mass to bring it to the consistency of a stiff paste which is then moldedr-into the desired shape or form needed. After the material is thus molded it is left to dry in the air until it becomes hard enough to handle when it is fired to a red heat and after cooling is ready for use. p

Preferably one part of clay, one part of iron and one-quarter part of carborundum' are the proportions required although these may be varied. accordingto the results desired. For instance, by increasing thequan- Specification of Letters Patent.

Patented Apr. 16, 1918.

Application filed-September 25, 1917. Serial No. 198,190.

tity of .carborundum a higher resistance is o-btainedand at the same time the percentage of decreasing resistance due to heating of the composition in use is increased. Under some circumstances when a relatively low resistance is required the carborundum may be omitted entirely but I prefer to employ it as it has the natural characteristic of lowering resistance under heat and being of very high resisting nature helps to increase the resistance of the clay and iron. The composition does not deteriorate in any man to go back into its original state, that is the resistance rises as the composition cools and even when belng heated to the fusing point the iron in this composition does not fuse.

Preferably the composition after it has been fired is sealed in tubes of non-combustible material so as to guard it against breakage. The action of this material is probably as follows: Whencurrent is passed through a stick of the materlal it follows through the iron in the-mixture and as the temperature rises this iron in the mixture expands, and expanding more rapidly than the clay creates a pressure tending to bring the iron While the above described composition may be used for many purposes I have found it particularly useful as a substitute for the assisted by .ner from use and has a tendency on cooling,

ordinary starting boxes of electrical motors,

employing it as a self-starter-by passing the current of the motor through it. Obviously, upon the first passage of current the composition-olfers great resistance so tively weak current is firstsupplied to the motor. As the current continues to flow through the composition the composition becomes gradually' more and more heated with the result that it offers less and less resistance to the current until the full strength of current is passing through it. Obviously, a suitable resistance of this character may be made much cheaper than the ordinary starting boxes and is superior in that it is autothat a i'elamatic in its action and, therefore, uniform,

whereas an operator may injure either the 1 motor or the=starting box by improper manipulation.

Having thus -described the invention, What is claimed as new is:

1. A. composition for the manufacture of electrical resistances including a binder in finely divided form, a metal in finely divided form, and carborundum in small grains 2. A composition for the manufacture of electrical resistances including a mixture of an electrically inert binder, a finely divided metal in metallic form, and carborundum.

3. A composition for use in the manufac ture of electrical resistances including a mix ture of finely pulverized clay, finely pulverized iron and carborundum.

4. A composition for use in the manufacture of electrical resistances including a mixture of one part of finely divided clay, one part offinely pulverized iron in metallic form, and one-quarter part of carborundum.

5. A composition for use in the manufacture of electrical resistances including an intimate mixture of finely divided clay and iron.

6. The method of manufacturing electrical resistances which consists in mixing finely divided clay, iron and carborundum, to-' molding the paste to the desired form and in firing the molded article.

7. The method of manufacturing electrical resistances which consists in mixing finely divided clay, iron and carborundum, together withwater to provide a' stifi paste, in moldin the paste to the desired form and in firing the molded article to a red heat.

8. The method of manufacturing electrical resistances which consists in forming an intimate mixture of finely divided clay, iron and carborundum in substantially the proportions of one part of clay to one part of iron and one-quarter part of carborundum, in adding Water, and in mixing the mass to form a paste, in'molding the paste to a suit-- able form and in firing. the article thus formed to a red heat.

9. The method of manufacturing electrical resistances which consists in mixing an electrically inert binder in finely divided form with a finely divided metal in metallic form and with carborundum, together with Water to provide a stifi paste, in molding the paste to the desired form, and in firing the molded article.

In testimony whereof I aflix my signature.

JOHN G. CLEMJNS. [L.s.] 

